The present invention relates generally to products and methods for providing fall protection systems for construction workers, maintenance workers, and others who work or walk upon elevated structures. More particularly, it relates to fall protection systems which employ safety stanchions mounted to the elevated structure so as to anchor and support safety cables.
During the construction of a bridge, building or other structure, it is common for workers to work and walk upon structural or architectural steel beams forming a part of the construction. Obviously, it is important but difficult to protect such workers and others from harm when they inadvertently slip and fall from elevated beams.
It is also important, for the purpose of controlling construction costs and facilitating rapid construction, that any fall protection system which is put in place to protect the workers be relatively inexpensive, relatively quick and easy to install, and later dismount, and cause little interference with the construction process itself.
Most conventional fall protection systems to which the present invention relates involve systems for supporting the worker with a safety cable that may be anchored and supported in various ways. Once a safety cable is anchored and supported, workers may obtain support by attaching themselves to the safety cable, as, for example, by way of a safety lanyard attached both to the cable and to a harness worn by the worker.
Unfortunately, in most superstructures where persons are called upon to walk and work upon elevated beams, there are few or no suitable anchoring points for attaching safety cables. Attaching the cables directly to the beams beneath the workers"" feet could increase the likelihood of tripping, and could also increase the potential fall distance.
Even if there are elevated anchoring points in the superstructure, the location of those points could cause the safety cable to extend directly above the very beam upon which the worker wishes to walk and work, thereby hindering the worker""s actions. In comparison to such anchoring points, it would be preferable, instead, to anchor a safety cable in such a way that, as the safety cable extends along the beam, it is suspended not just above the beam but also off-set slightly to one side of the beam, so that it will not unnecessarily hinder the worker as he or she works upon or walks along the beam""s upper surface.
A means of providing fall protection with such an elevated but off-set cable positioning is disclosed in U.S. Pat. No. 5,307,897, wherein a safety stanchion employs both a first and a second lock means, with the first lock means depending upon properly torqued bolts (which could be subject to failure from loss of friction if worn or insufficiently tightened), and with the second lock means being mounted to a post and being somewhat complex, comprising, for example, a ratchet lock mechanism comprising a strap made of nylon or another synthetic material (which sunlight, chemicals or a nearby heat source, such as nearby welding, could render subject to failure). That previously disclosed safety stanchion is preferably used with a safety cable having an in-line shock absorber.
U.S. Pat. No. 6,173,809 (the ""809 patent) which discloses an invention of which I am a co-inventor also provides a safety stanchion with an elevated and preferably off-set cable positioning. However, it does so with various other means, none of which, for example, require a ratchet lock mechanism or a nylon or synthetic strap as shown in the aforementioned art. The invention of the ""809 patent also provides a safety stanchion having a post that preferably can, by flexing and by permanently deforming without failing, reduce and absorb at least some of the shock and sudden loading caused by a worker""s fall from a beam, without the need for a safety cable having an in-line shock absorber.
As previously noted, there are advantages to be gained by providing a fall protection system that is relatively inexpensive, that may be quickly and easily mounted to and dismounted from an elevated beam, and that will support and anchor a safety cable above and slightly to the side of the elevated beam. The invention of the ""809 patent teaches such a safety stanchion.
One embodiment of the invention of the ""809 patent provides a safety stanchion for mounting upon a surface such as structural I or H shaped beam which are typically found in the superstructure of a bridge, a building or some other structure being built.
This safety stanchion includes a tapered tubular post having a lower end for attachment to a support base at preferably an oblique angle and an upper end for supporting a safety cable and the like. Due to its tapered shape, the post""s upper end has an outside diameter which is less than that of its lower end. The post also preferably has a wall thickness of less than 0.125 inches and is frustoconically shaped. In addition, the post is preferably made out of an energy absorbing, elastic-like, high strength steel such as A595 grade steel which in cooperation with the post""s wall thickness and tapered, preferably frustoconical, shape is believed to render the post capable of inelastically deforming before it fails, thereby better able to break a worker""s fall without actually breaking in half. Fail or failure of the post as used herein refers to a post which has actually broken or buckled to a point where it is no longer capable of providing any significant resistant to lateral forces or other forces tending to cause bowing of the post.
As will be appreciated, the attachment of the post""s lower end to its base at an oblique angle enables the suspension of safety cables above, but slightly to the side, of the particular beam or surface upon which the safety stanchion is mounted.
The stanchion also preferably includes a cap, having two bores, which is firmly secured to the upper terminus of the post, and by means of which safety cables can be easily attached to the tapered tubular post, and therefore to the safety stanchion itself, such as with simple, conventional devises.
In the preferred safety stanchion of this type, the tapered post is capable of flexing and permanently (or inelastically) deforming without failing, in response to sudden loads (within its design limits) that might occur when a person who is attached to the stanchion via a conventional safety cable falls from an elevated beam or similar surface upon which the stanchion is mounted.
The invention of the ""809 patent also provides a unique base or base assembly for mounting a stanchion upon a structural member such as an I beam, H beam or other structural member having flange portions, regardless of the, structural member""s orientation to the horizon, i.e. vertical, horizontal or other disposition. In its broadest sense, the base has a mounting assembly or means which includes first jaw means for engaging a first portion of a structural beam and opposing second jaw means for engaging a second portion of the beam. The mounting assembly also includes right and left rod assemblies which respectively cooperate with the first and second jaw means for drawing the jaw means together to clamp a beam, typically the flange portions of a structural beam which extend outwardly from the center section of a typical structural I or H beam. The rod assemblies are preferably oriented with respect to each other so that their longitudinal axes converge towards each other. A preferred angle of convergence may extend up to 90 degrees as measured by the included angle defined by the longitudinal axes of the rod assemblies.
As used herein, converge means to draw closer to or approach each other and such converging, non-parallel positioning of the rods enables better clamping of the beam. Specifically, the converging rods are believed to be better able to resist both twisting and longitudinal motion along the beam (sometimes called xe2x80x9cwalkingxe2x80x9d), in response to vibration, twisting or other forces during the arrest of a worker""s fall.
In a preferred embodiment of the invention of the ""809 patent, the rod of each rod assembly is provided with aggressive threads on the order of 3 to 7.5 threads per inch for cooperating with complementary threaded first and second internally threaded members which in turn respectively cooperate with the first and second jaw means of the mounting assembly to clamp a structural beam when one of the internally threaded members, preferably a wing nut, is tightened by threading it in a direction which causes the jaw means to draw together and clamp a beam disposed between the jaw means. The aggressive threads enable a workman to install the stanchion on a beam very quickly since they cause the jaw means to close and thereby clamp a beam disposed between the jaw means with only a few turns of one of the internally threaded members.
Another safety stanchion of the invention of the ""809 patent for mounting on a structural beam and the like has a sleeve on the stanchion""s base for slidably receiving an end of the stanchion""s post. Fastening means such as set screw type bolts are also provided for securing the post""s end in the sleeve when it is slidably received therein. The sleeve may be integral with the base or rigidly affixed to the base for example by welding it to the base. The sleeve may also be positioned or oriented on the base so that the base may be mounted upon either vertically disposed I beams, i.e. columns, or horizontally disposed I beams. A typical post used in conjunction with this base is L-shaped and as shown in the drawings the lower end of the L-shaped post is slidably received in the sleeve.
In addition and as will be appreciated, all safety stanchions of the invention of the ""809 patent provide an effective fall protection system, which is lightweight, simple, relatively unaffected by sunlight, chemicals and indirect heating, relatively quick and easy to mount upon a beam by hand or with a simple tool, capable of supporting and anchoring safety cables above but to the side of the mounted beam, where they will not unnecessarily hinder a worker on the beam, inherently able to reduce and absorb, through flexion and through permanent deformation, some of the shock and sudden load caused by a worker""s fall from the beam, and better able to resist twisting and longitudinal motion upon the beam.
While the invention of the ""809 patent is easily attachable to I beams and other structural members, a need still exists for a safety stanchion which is directly and easily attachable to a concrete structure. In addition, a need exists for apparatus and methods for attaching existing I beam mounted safety stanchions to concrete.
The present invention builds upon the invention of the ""809 patent and the prior art by providing a unique safety stanchion for mounting directly to concrete. The unique stanchion includes a post having first and second ends, means for supporting a safety cable at said first end of said post and a base attached to the second end of the post for mounting the post on a flat surface of a concrete structure. The base includes a mounting plate having a generally flat bottom surface for placement against the flat surface of the concrete structure as well as a top surface and a plurality of holes extending through the plate from the bottom surface to the top surface.
In addition, the present invention provides several apparatus and methods for mounting any type of safety stanchion to concrete including the stanchions of the ""809 patent, the prior art and the unique safety stanchion of the present invention for being mounted directly to concrete.